Alternative Fuel Burner with Plural Injection Ports

ABSTRACT

A burner or furnace including a combustion chamber and two or more fuel injection ports. The fuel injection ports inject fuel at non-radial injection angles into the combustion chamber. Preferably, the injection ports feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation. Also preferably, the injection ports are angled downward 5 to 15 degrees from a plane perpendicular to an axis of the burner or furnace.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/913,450, filed Apr. 23, 2007, entitled “Alternative Fuel Burner with Plural Injection Ports,” in the name of Charles Verhoff

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an alternative fuel burner with plural injection ports.

2. Description of the Related Art

The Onix Corporation offers a full line of industrial wood combustion burners rated to a maximum of 120 million Btu/hr. These cyclonic burners offer a wood energy alternative clean enough to rival natural gas emissions. The response time of these burners is able to control many fragile operations, such as: dryers, boilers, rotary kilns and industrial air heaters. The combustion of solid fuel yields way to a world of low-cost, environmentally sound fuels. Existing burners can be retrofitted to enable industries the option of burning gas, liquid or solid fuels.

These burners are capable of delivering between 400,000 and 120 MM Btu per hour, and can achieve temperatures of 2,000° F. while saving money on every Btu used. The Onix Corporation's full line of Solid Fuel Burners have many industrial applications including retrofitting natural gas burners, dryer heat source, heat for kilns, heat source for boilers, as well as winter time industrial space heating.

These solid fuel systems can operate on a number of alternative fuel materials: bagasse, charcoal, coal, corn, corncobs, dried peat moss, dried wood chips, horse manure, paper, sawdust, shavings, thermoplastics, thermosetting plastics, wood flour, wood waste, etc. yielding fuel costs of below $1.00/MM Btu.

Cyclonic furnaces have become a major alternative to conventional burners. Applications include both large scale utility boilers and certain industrial processes where waste heat can be recovered profitably. The Onix Series Solid Fuel Burner is operated by the method of “cyclonic combustion.” In cyclonic combustion, the burning occurs at a positive pressure, rather than the slight negative pressure associated with most suspension fired wood systems.

The combustion occurs in specially designed cylindrical reactors which discharge hot gaseous combustion products directly into the boilers or other vessels. Pulverized wood is blown into the cyclonic burner where it oxidizes immediately. Centrifugal action forces the particles toward the cylindrical wall of the burner where char oxidation occurs. Very high turbulence is generated in the cyclonic burner and char oxidation occurs within milliseconds.

Combustion intensity in cyclonic burners is considerably higher than combustion intensity in conventional wood suspension fired furnaces. The vigor of the cyclonic action forces the wood particles to the burner wall, facilitating not only rapid combustion but also solid product removal. Cyclonic burners typically remove 99% of the solid products of combustion. These solid products of combustion (to small to be visible) are entrained into the air stream and then enter the boiler or other vessel, where they are removed as flyash by a particulate control system.

SUMMARY OF THE INVENTION

The invention relates to an improvement on the burners and furnaces described above. In particular, an embodiment of the invention includes two or more fuel injection ports. The injection ports inject fuel at non-radial injection angles. Preferably, the injection ports feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation. The injection ports preferably are also angled downward 5 to 15 degrees from a plane perpendicular to the axis (or axes) of the burner or furnace. Other injection angles can be used.

In some embodiments, the injection angles for all of the ports are the same. In other embodiments, the injection angles for different ports are different. The injection angles can be fixed or adjustable. Adjustable injection angles are preferred, for example to allow for adjustment to maximize efficiency and to match different types of fuels.

These arrangements tend to lead to significantly improved performance in the PM/PM10, SOx, NOx, and CO categories (i.e., lower emissions of pollutants). In some cases, emission of pollutants is unexpectedly and drastically reduced.

This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention may be obtained by reference to the following description of the preferred embodiments thereof in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 show one embodiment of the invention.

FIGS. 5 to 11 show some but not all possible alternative embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention relates to an improvement on the burners and furnaces described above. The burner uses two or more fuel injection ports to accomplish unprecedented NOx emissions (preferably lower than 35 ppm NOx) for solid fuel burners.

In particular, an embodiment of the invention includes two or more fuel injection ports. The injection ports inject fuel at non-radial injection angles. Preferably, the injection ports feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation. The injection ports preferably are also angled downward 5 to 15 degrees from a plane perpendicular to the axis (or axes) of the burner or furnace. Other injection angles can be used.

A plural injection port low NOx burner according to the invention accomplishes unprecedented NOx emissions (preferably lower than 35 ppm NOx) for solid fuel burners. Biomass fuel preferably is first dried to less than 10% moisture and ground in a hammermill to below a ⅛″ particle size. In a preferred embodiment, the fuel is fed on demand to the solid fuel burner and injected tangentially at a downward angle between 5 and 15 degrees. The fuel and combustion air can enter at multiple locations through one or more pairs of approximately 180 degree offset injection ports. In a preferred embodiment, the fuel to air ratio yields a resulting flue gas composition of ˜3% O2, CO of ˜0 ppm and NOx of below 35 ppm. Flue gas recycle FGR can also be used to reduce the NOx ppm. (Of course, the invention is not limited to embodiments that achieve these results.)

In some embodiments, the injection angles for all of the ports are the same. In other embodiments, the injection angles for different ports are different. The injection angles can be fixed or adjustable. Adjustable injection angles are preferred, for example to allow for adjustment to maximize efficiency and to match different types of fuels.

In more detail, FIGS. 1 to 4 show an embodiment of a burner with a combustion chamber that has a circular cross section and two fuel injection ports. As shown in FIGS. 1 and 2, the injection ports preferably feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation. As shown in FIGS. 3 and 4, the injection ports preferably are also angled downward 5 to 15 degrees from a plane perpendicular to the axis (or axes) of the burner or furnace. The invention is not limited to these injection angles or even to downward injection of the fuel.

In more detail, FIGS. 1 to 4 show burner 1 with combustion chamber 2 having refractory wall 3 to contain heat from combustion within the chamber. FIG. 1 is a top-down view, FIG. 2 is a cross-section view, and FIGS. 3 and 4 are side views.

In these figures, fuel line 4 feeds fuel and combustion air into combustion chamber 2 through injection ports 5. Other arrangements for feeding fuel to the injection ports can be used.

Burners according to the invention are particularly suited to burning alternative and biomass fuels. Examples of such fuels include, but are not limited to bagasse, charcoal, coal, corn, corncobs, dried peat moss, dried wood chips, horse manure, paper, sawdust, shavings, thermoplastics, thermosetting plastics, wood flour, and wood waste. In the case of biomass fuels, the biomass preferably is first dried to less than 10% moister and ground in a hammermill to have a particle size less than ⅛″. The invention is also applicable to burners and furnaces that burn conventional fuels such as natural gas, fuel oil, palletized or other forms of coal, and the like.

Preferably, fuel and combustion air are fed into the burner on demand and injected tangentially at a downward angle between 5 and 15 degrees, as discussed above. The fuel and combustion air preferably are injected at multiple locations through one or more pairs of injection ports. In a preferred embodiment, the injection ports of each pair are offset from each other by 165 to 180 degrees, with pairs offset by closer to 180 degrees more preferred. Injection port pairs offset by less than 165 degrees also can be used.

When the burner is in operation, burning fuel from the injection ports forms a cyclonic combustion vortex within the burner. This vortex is illustrated in FIG. 2 by arrow 7 and in other figures by similar arrows.

The cyclonic combustion vortex preferably is contained by refractory wall 3. Injection ports 5 preferably feed fuel substantially tangentially into the cyclonic vortex. In this context, “substantially” indicates that the fuel is feed tangentially enough so that the injected fuel flows with and into the cyclonic vortex, not perpendicular to or against the vortex. In a preferred embodiment, the fuel flows completely tangentially into the cyclonic vortex. In alternative embodiments, the fuel can flow from the injection ports into the vortex at an angel of 5 or 10 degrees from the tangent, or at an even greater angle.

Fuel burned by the resulting cyclonic combustion vortex tends to burn hotter, cleaner, and quicker than fuel burned in conventional burners, thereby tending to lead to significantly improved performance in the PM/PM10, SOx, NOx, and CO categories (i.e., lower emissions of pollutants). In some cases, emission of pollutants is unexpectedly and drastically reduced.

As shown in FIGS. 3 and 4, injection ports 5 preferably are also angled 5 to 15 degrees downward from a plane perpendicular to the axis (or axes) of the burner. This downward angle counteracts up-flow caused by the high level of heat in the vortex, helping to keep the vortex contained within the burner and tending to further improve performance. A downward angle of 15 degrees has been found to give exceptional results in some cases. Of course, the invention is not limited to these downward angles.

Most fuels require an oxidizer in order to burn, for example but not limited to oxygen in air. This oxidizer preferably is mixed with the fuel before being fed by the injection ports into the furnace. In some embodiments, additional air or another oxidizer can be fed into the combustion chamber through intake port 8 shown in FIGS. 3 and 4. This additional air or other oxidizer can be drawn into the combustion chamber by the cyclonic combustion vortex. Alternatively, a different arrangement for introducing an oxidizer can be used. One example includes vents on a bottom of the combustion chamber. Other structures can be used for this purpose. In addition, some fuels include their own oxidizer. Burners designed for those fuels can be implemented without intake port 8 and/or other structures for introducing an oxidizer.

FIGS. 3 and 4 show additional optional structures, namely view port 9 for viewing an interior of the burner, access port 10 for removal of ash and other maintenance of the burner, and chimney 11. Additional elements also can be included, for example an ignition mechanism for starting fuel to burn in the combustion chamber, a particulate control system, and the like.

FIGS. 5 to 11 show some but not all possible alternative embodiments of the invention.

FIG. 5 shows burner 12 with combustion chamber 13 that has an elliptical cross section. Other shaped combustion chambers can be used.

FIG. 6 shows burner 14 with more that two injection ports 15. FIG. 7 likewise shows burner 16 with more than two injection ports 17. FIG. 7 also illustrates that different ones of injection ports 17 can have different injection angles.

FIG. 8 shows burner 18 with injection ports 19 at different heights. FIG. 8 also illustrates that the injection ports can have different down angles or even up angles from a plane of a cross section of the combustion chamber.

Similar to FIG. 8, FIG. 9 shows burner 20 with injection ports 21 at different heights. This figure also illustrates that an injection angle for one or more of the injection ports can be adjustable. This is illustrated in the figures by a small circle where an injection port enters a combustion chamber. FIGS. 10 and 11 show that one or more of the injection angles for injection ports 22 and 23 also can be adjustable with respect to their alignment with the cyclonic combustion vortex in the burners.

Each of the various features shown in the figures can be used in conjunction with any of the other features shown in the figures. Furthermore, the invention encompasses other shapes of burners and arrangements of injection ports besides those shown in the figures.

Alternative Embodiments

Burners according to the invention can be larger or smaller than those discussed above. Furthermore, the invention is in no way limited to the specifics of any particular embodiments and examples disclosed herein. For example, the term “burner” was used throughout the description of the figures. However, the invention and angled fuel injection ports are equally applicable to furnaces, boilers, and any other types of apparatuses that include combustion chambers. In addition, the terms “preferably,” “preferred embodiment,” “one embodiment,” “this embodiment,” “alternative embodiment,” “alternatively” and the like denote features that are preferable but not essential to include in embodiments of the invention. The terms “comprising” or “including” mean that other elements and/or steps can be added without departing from the invention. Many other variations are possible which remain within the content, scope and spirit of the invention, and these variations would become clear to those skilled in the art after perusal of this application. 

1. A burner or furnace, comprising: a combustion chamber; and two or more fuel injection ports; wherein the fuel injection ports inject fuel at non-radial injection angles into the combustion chamber.
 2. A burner or furnace as in claim 1, wherein the injection ports feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation.
 3. A burner or furnace as in claim 1, wherein the injection ports are arranged in one or more pairs, with the injection ports of each pair offset from each other by 165 to 180 degrees.
 4. A burner or furnace as in claim 1, wherein the injection ports are angled from 5 to 15 degrees from a plane perpendicular to an axis of the burner or furnace.
 5. A burner or furnace as in claim 1, wherein the injection angles for all of the fuel injection ports are the same.
 6. A burner or furnace as in claim 1, wherein the injection angles for different fuel injection ports are different.
 7. A burner or furnace as in claim 1, wherein one or more of the injection angles are fixed.
 8. A burner or furnace as in claim 1, wherein one or more of the injection angles are adjustable.
 9. A burner or furnace as in claim 1, wherein a cross section of the combustion chamber is circular.
 10. A burner or furnace as in claim 1, wherein a cross section of the combustion chamber is non-circular.
 11. A method of burning fuels, comprising the steps of: starting burning in a combustion chamber; and injecting fuel into the combustion chamber using two or more fuel injection ports; wherein the fuel injection ports inject fuel at non-radial injection angles into the combustion chamber.
 12. A method as in claim 11, wherein the injection ports feed fuel substantially tangentially to a cyclonic vortex in the burner or furnace during operation.
 13. A method as in claim 11, wherein the injection ports are arranged in one or more pairs, with the injection ports of each pair offset from each other by 165 to 180 degrees.
 14. A method as in claim 11, wherein the injection ports are angled from 5 to 15 degrees from a plane perpendicular to an axis of the burner or furnace.
 15. A method as in claim 11, wherein the injection angles for all of the fuel injection ports are the same.
 16. A method as in claim 11, wherein the injection angles for different fuel injection ports are different.
 17. A method as in claim 11, wherein one or more of the injection angles are fixed.
 18. A method as in claim 11, wherein one or more of the injection angles are adjustable.
 19. A method as in claim 11, wherein a cross section of the combustion chamber is circular.
 20. A method as in claim 11, wherein a cross section of the combustion chamber is non-circular. 